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Steve Crandall's Squash Stringing Tips

Zyex® Squash String Design and Performance

By Steve Crandall
Vice President, Sales & Marketing
Ashaway Racket Strings


Squash Family
To date there have been two primary Zyex combinations that work very well in squash strings. One is a Zyex multifilament core construction used in our UltraNick® family of strings. Multifilament construction adds sheer strength to the core and reduces the liveliness of the strings just enough to deliver what we call "soft power."   The other is our PowerNick® family, which uses a single large monofilament surrounded by a number of slightly thinner monofilaments to generate "hard power;" a crispness, or pop, that sensation of the ball leaping off the racquet the instant it strikes.
In this and the next column we're doing for the February issue, I'd like to connect the dots between two major raw materials used in squash strings - nylon and Zyex® - and the performance of the string designs that result. Think of it as a kind of 'what can you do for me?' overview of the plusses and minuses of the materials, the ways we are able to use them, and what they may (or may not) do for you when you put them in your racquet. We'll start with Zyex.

Zyex is the trade name for a high temperature, engineering grade polymer known as polyetheretherketone, polyketone or just PEEK. Polyketone materials like Zyex have several physical properties of interest to manufacturers. PEEK monofilaments and fibers are very tough and durable, and have excellent abrasion resistance. In tests measuring "thread on thread" abrasion conducted at room temperature, PEEK multifilaments outlasted aramid fibers by a factor of approximately 5.5. PEEK also has very low moisture uptake at 0.1%, which means you don't need to worry about playing in humid conditions or near the equator in spots like Key West, Darwin, and Singapore.

The property that makes Zyex so good for racquet strings is its low dynamic stiffness, which allows them to stretch and recover more completely than other synthetic materials. This generates power with low impact shock (soft power). Zyex can also be made to have exceptionally low creep under continuous tension, allowing racquet strings to maintain tension and playability longer.

We've experimented with Zyex in a number of different ways in designing racquet strings for squash, racquetball, tennis and badminton. Some work well in some sports but not in others; some do work well in all; and others, well, not so much anywhere - but we don't make any of those!

For example, Zyex monofilaments work very well in tennis strings, generating exceptional power and spin without the bone-jarring shock of poly or copoly monofilaments. However, they are too lively to work with lightweight squash balls, causing loss of control, and do not have the durability to deal with the high number of off-center hits in racquetball.

To date there have been two primary Zyex combinations that work very well in squash strings. One is a Zyex multifilament core construction used in our UltraNick® family of strings. Multifilament construction adds sheer strength to the core and reduces the liveliness of the strings just enough to provide optimum power and control. The 17 gauge version provides superior power and durability, while the 18 gauge version provides a bit more feel. Both offer exceptional tension retention and deliver what we call "soft power."

Our PowerNick® family, on the other hand, generates "hard power." What we mean by "hard power" is crispness, or pop, that sensation of the ball leaping off the racquet the instant it strikes. Where UltraNick will stretch a bit before rebounding, PowerNick strings are stiffer and rebound faster, driving the ball.

We achieve this by using what we call a multi-stranded Zyex monofilament core. This is a single large monofilament surrounded by a number of slightly thinner monofilaments, all encapsulated with a high-tenacity monofilament nylon wear surface, textured to provide optimum ball response and spin characteristics. Of the two gauges available, PowerNick 18 (1.15 mm) is designed to provide optimum power and resilience, and PowerNick 19 - which at 1.05 mm is the thinnest squash string ever made - offers superior power and ball control.

Most recently, we have been experimenting with weaving Zyex fibers into the jacket or wear layer of multifilament nylon strings. Jackets are designed to hold core packages together, increase abrasion resistance, and sometimes add surface texture to increase bite on the ball. However, when we tried weaving Zyex fibers into jacket constructions, we found they enhanced string playability as well.

So good is this new construction, in fact, that we trademarked it as PFTTM (Power Filament Technology) and will build a new SuperNickTM ZX family of strings around it. PFT jackets on a multifilament nylon core add power, improve tension holding, and increase string durability. What you get, in effect, is a nylon-based string with superpower, i.e., Zyex power. But more on that later.

For now, there are two Zyex choices for squash. If you like the softer feel of nylon, but want more power and better tension holding, try an UltraNick string. If you like the power and feel of unbridled Zyex, go with a PowerNick model. If you want something entirely new, stay tuned.

ZYEX® is a registered trademark of Victrex Ltd.
This article previously appeared in Squash Magazine.


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